I like this topic. I can talk for hours and hours on this.
My $0.02.
- Wei Yan was an excellent general. Most of KongMing's success are really due to this braveness and execution. Like Sima Yi, KongMing is the overall commander, and hence not always at the front-line. KongMing and Sima Yi sets overall strategies and worry about operational stuff like chasing up food/supplies etc, whereas Wei Yan was the guy who really did all the day-to-day fighting and the dirty work. Many times KongMing sends a message to Wei Yan saying 'watch for Wei attack tonight', or 'check for ambush before advancing', only Wei Yan knew how to execute everytime without flaws.
- Wei Yan is extremely loyal to Liu Bei. He might have served different lords but so as Guan Yu, Zhao Yun, Zhang Liao, Tai Shi Chi, Jiang Wei....oh the list goes on. He has contributed many success to Shu and has been one of the key Shu general ever since Liu Bei took the Shu province.
- Wei Yan is a on-the-ground leader. If he is a modern day general he'll be the type that you'll see drinking beer/throwing darts at a pub with 'his boys', as he would prefered to call his soilders. He is arrogant about his strength and his army, and certainly does not get along with the accounting guys from 'the head office'. One of the accounting guys was Yang Yi. They have been known to have furious arguments, and that one time when it got heated, Wei Yan took out his knife, shuff it next to this nose and ask Yang Yi whether he can smell blood stinks from shaving off heads of thousands Wei soilders. Yang Yi begged for his mercy and started crying. KongMing saw all this, shake his head, and told them both to go cool off. In truth, there was little KongMing can do. He needed Wei Yan and he needed Yang Yi.
- Just before KongMing knew he was about to pass away, he left instructions for Wei Yan to protect Shu's retreat. He specifically asked that Wei Yan to 'reverse their flags' and attack if Sima Yi comes and checks on the retreat. He left these instructions because he knew Sima Yi had no intention to engage, but only to see whether Shu's leaving in a rush. Indeed, Sima Yi have been in hiding for the past 6 months and have not engaged Shu at all even if KongMing sends him woman clothing. He left the control of the main army to Yang Yi.
- Knowing his past history with Wei Yan, Yang Yi send Fei Wei to the front-camp to deliver the message to Wei Yan. At that time Fei Wei was one of the up-and-commers in the government rank so it is obvious that Yang is trying to give as much 'face' to Wei as possible. Upon hearing the message, Wei Yan was furious. He doesn't understand why they are retreating. He's thinking, 'Didn't we just kill three thousand Wei soilders a month ago? They are scared to death! He questioned further whose idea was this, and Fei Wei let it slipped that Yang Yi is now running the show. What?! that little bastard who drooled on my knive? That's it something is wrong. The Prime Minister must be confused during his last hours and was bewitched by the bastard. I must make things right before Shu's downfall. Now that Prime Minister is no longer here only I can continue in his path'
- He gave order to his camp to start packing. 'Where we going boss?'. He thinks about his options. He can certainly go join Wei. He's killed many of their soilders, but to desmonstrate to the rest of the world that Wei's a great kingdom, they'll welcome him greatly and probably send him to attack Shu. He'll get his revenge against Yang Yi there....but instead of that, he gave orders to take the much more dangerous, much longer way and go around the main Shu camp. My guess is he wanted to explain to Liu Chan himself and declare his intention, and also warn Liu Chan about Yang Yi. He knows that the main army might/will catch up with them, so he also orders his army to burn the road once they have passed thru. He's thinking if I hurry I can make it back to Liu Chan before Yang Yi...I'll be in trouble but the lord would understand. We'll regroup and have another go at Wei again.
- The main army finally caught up. Wang Ping lead the charge and accused the soilders underneath Wei Yan for treason...and the soilders panicked. They did not understand what they were doing, and they certainly did not want to fight aginst their own. One by one they left. Only then Wei Yan realised what he has done. There is nothing he can do now. Wei would no longer welcome him and Liu Chan was never going to 'understand'. He hide out in the mountain and hope to figure out his next move. Before long he was arrested by Ma Dai. His small glimpse of hope of explaining everything to Liu Chan was vanquished, when he knows that Yang Yi has ordered to execute him on the spot. He thinks about his family, the Prime Minister, his boys...but its all too late.
- Yang Yi returned to Shu as a hero. He's thinking about what he might do next...prime minister? He's already making plans about Shu's next military campaign. Suddenly message came that, under the last orders of Zhuge Liang, Zhang Yun was now the Top General and would take control of the government. Furthermore, Zhuge Liang also specified Fei Wei was to follow Zhang Yun, and Dong Wan was after Fei....he didn't even make the list. He finally understood that Zhuge Liang never had bigger plans for the accounting guy. He's devastated. 'Who's Zhang Yun anyway? We probably should have joined Wei if we had the chance' he commented to Fei Wei once when he was looking for another loser's shoulder to cry on, wrongly thinking that Fei might be just as devastated as he is. Fei has never heard such rediculous comments in his life from a high government official, and he had no choice but to report it to Liu Chan. Liu Chan got the easiest task of that day. He sent Yang Yi off to the chops, and went back to bed.
- In my opinion Wei Yan is one of the greatest generals in the 3k era. But due to his hot-headedness, he dug and even hammered in the nails on his own grave.